The present invention relates to a pneumatic radial tire for heavy loads having a block type tread pattern, and more particularly to a pneumatic radial tire for heavy loads having improved uneven wear resistance and steering stability without lowering traction performance specific to the block type pattern.
In order to secure a good traction performance on wet roads or snow-covered roads for a pneumatic radial tires for heavy loads, it is well known that it is effective to employ a block type tread pattern. However, when the tread pattern is based on a block design, tread rigidity tends to decrease due to a block construction. And it causes each block to slide on the road upon braking or driving, so that uneven wear such as heel-and-toe abrasion which involves different amounts of wear between the frontal and rear edges in each block in the rotation direction of the tire readily occurs, and also steering stability is lowered.
Therefore, in order to prevent the uneven wear from taking place and the steering stability from lowering, countermeasures such as providing shallow grooves around blocks have been taken heretofore. According to the above countermeasures, however, there has been such a problem that part of the grooves disappear before a complete wear of the tread takes place, thereby lowering the traction performance.